Asynchronous and Synchronous Communication in College English Writing in Web-based Learning Environment

In web-based learning environment,College English writing has always been a thorny issue.Here both asynchronous and synchronous communications in college English writing mean the new interactive teaching belief. This paper attempts to do the blending of two in the traditional writing learning and teaching in college English in order to promote a more flexible,efficient and interactive learning environment in accordance with students' interests and needs.

Secure communication based on spatiotemporal chaos

In this paper, we propose a novel approach to secure communication based on spatiotemporal chaos. At the transmitter end, the state variables of the coupled map lattice system are divided into two groups: one is used as the key to encrypt the plaintext in the N-shift encryption function, and the other is used to mix with the output of the N-shift function to further confuse the information to transmit. At the receiver end, the receiver lattices are driven by the received signal to synchronize with the transmitter lattices and an inverse procedure of the encoding is conducted to decode the information.Numerical simulation and experiment based on the TI TMS320C6713 Digital Signal Processor(DSP) show the feasibility and the validity of the proposed scheme.

Internet-based event synchronization communication driven telerobotics

Based on QoS (quality of service) parameters: time delay, jitter, bandwidth and package loss. As time delay in the Internet is variable, it is hard to compensate it by traditional methods. Event synchronization communication driven method is proposed to overcome the negative effects induced by time delay. This method is a non-time based method and it can get rid of the effects of time in the control loop of telerobotics. Stability, transparency and synchronization can be maintained in it by event-driven method. Multimodal enhanced telerobotics is put forward with its feedback including force, video, audio and temperature etc. The use of multimodal feedback improves the efficiency and safety of the whole system. Synchronization in multimodal feedback is hard to ensure and event-driven method is also good for it. Experiments on an Internet-based shaft-hole assemblage system show good results by using event synchronization communication driven method and UDP protocol.

Investigation on full distribution CNC system based on SERCOS bus

A full distribution CNC system based on SERCOS bus is studied in accordance with the limitations of traditional PC-based motion card. The conventional PC-based motion control card is dispersed into several autonomous intelligent servo-control units with the function of servo driver. The autonomous intelligent servocontrol units realize the loop control of position, velocity and current. Interpolation computation is completed in PC and the computational results are transferred to every autonomous intelligent servo-control unit by high speed SERCOS bus. Software or hardware synchronization technology is used to ensure all servomotors are successive and synchronously running. The communication and synchronization technology of SERCOS are also researched and the autonomous intelligent servo-control card is developed byself. Finally, the experiment of circle contour process on a prototype system proves the feasibility.

Timed-pNets： a communication behavioural semantic model for distributed systems

This paper presents an approach to build a communication behavioural semantic model for heterogeneous distributed systems that include synchronous and asynchronous communications. Since each node of such system has its own physical clock, it brings the challenges of correctly specifying the system time constraints. Based on the logical clocks proposed by Lamport, and CCSL proposed by Aoste team in INRIA, as well as pNets from Oasis team in INRIA, we develop timed-pNets to model communication behaviours for distributed systems. Timed-pNets are tree style hierarchical structures. Each node is associated with a timed specification which consists of a set of logical clocks and some relations on clocks. The leaves are represented by timed-pLTSs. Non-leaf nodes （called timed-pNets nodes） are synchronisation devices that synchronize the behaviours of subnets （these subnets can be leaves or non-leaf nodes）. Both timed-pLTSs and timed-pNets nodes can be translated to timed specifications. All these notions and methods are illustrated on a simple use-case of car insertion from the area of intelligent transportation systems （ITS）. In the end the TimeSquare tool is used to simulate and check the validity of our model.

Frame synchronization for underwater acoustic communication based on maximum likelihood estimation

Traditional frame synchronization methods for underwater acoustic communication(UWAC) merely depend on correlation coefficient when synchronization signal detection is concerned and,hence,false triggering and missed synchronization can hardly be avoided in complex UWAC channels.In order to solve this problem,firstly,we analyze the effects of interference from noise,multipath and Doppler on frame synchronization;then we propose a new frame synchronization scheme based on parameter estimation.By exploiting the parameter estimation technique,we detect the synchronization signal according to the estimated parameters,thus the false triggering rate and missed synchronization rate can be reduced.We also simplify the maximum likelihood estimation to reduce computational cost.Simulation results indicate that this new scheme outperforms the traditional method in terms of delay resolution and correlation coefficient.Both static and mobile communication experimental results show that the correlation coefficient of the new scheme is higher than that of the traditional one.Moreover,the detection ability of the receiver is improved,which helps to avoid false triggering and missed synchronization.

Chaos－Shift－Keying Secure Digital Communications Using Feedback to Synchronize Chua＇s Circuit

in this paper a chaotic secure communication System using a feedback controlling subsystem is presented.The transmitter and the receiver are built with Chua's circuits.We find that,using feedback controlling,the time for the receiver to obtain the Synchronization with the transmitter can be obviously decreased.Thecorrelation between the time and the feedback coefficient is presented at the end of this paper.

Rendezvous Facilities in a Distributed Computer System

The distributed computer system described in this paper is a set of computernodes interconnected in an interconnection network via packet-switching interfaces.The nodes communicate with each other by means of message-passing protocols. Thispaper presents the implementation of rendezvous facilities as highlevel prhoitives provided by a parallel programming language to support interprocess cornmunication andsynchronisation.